Reproductive effort was manipulated in a free–living population of house sparrows (Passer domesticus) to investigate the trade–off between reproductive investment and the expression of a condition–dependent sexually selected ornament. Phenotypic plasticity in the expression of this trait was related to the experimentally manipulated size of the brood reared by a male. Males that invested more in current reproduction subsequently became more attractive to females in this population as they showed a preference for males with smaller badges. This supports the argument that direct benefits are a primary focus for mate choice by females. Trade–offs between reproductive effort and the expression of sexual ornaments are a potentially important source of phenotypic variation in both sexual ornaments and lifehistory traits.